Paraffin wax composition



i atented July 21, 19553 PARAFFKN WAX COMPOSITION Robert G. Capell,William P. Ridenour, and John A. Stewart, Pittsburgh, Pa., assignors toGulf Research & Development Company, Pittsburgh, Pa., a corporation ofDelaware No Drawing. Application June 30, 1950, Serial No. 171,528

6 Claims. 1

This invention relates to improved paraflin wax compositions, and moreparticularly to improved parafiin wax compositions stabilized againstoxi dative and analogous forms of deterioration resulting fromsubjecting paraffin wax to elevated temperature, air, and the like.

The methods of separating paraflin wax from crude petroleumproducts,'such as by distillation, chilling with filtering orcentrifuging, sweating, and solvent extraction, are well known. Variousmethods of parafi'in wax purification, such as treatment with sulfuricacid and fullers earth, are also well known. Although this purificationhelps to produce more stable paraflin waxes initially free from odor,taste, and color, it is not effective enough to preventsubsequentoxidative deterioration which has beentroublesome toindustrial users of parafiin wax.

One of the most Widely practiced applications of paraffin wax is in thecoating industry wherein hot Wax baths are employed for waterproofing,treating, impregnating or sizing paper and similar products, and whereinwax is employed to provide a protective coating for materials of allkinds. More specifically, the use of hot liquefied wax is widelypracticed in the manufacture of such articles as waxed paper, especiallywaxed bread wrappers, waxed milk cartons and other beverage containers,cartons, bottle caps, shot shell tubes, matches, wax impregnatedfabrics, paper-metal foil electrical condensers, junction and terminalboxes, transformers, Wax impregnated insulation, coils and windings,candles, as well as a host of other products too numerous to mention.

In each instance where a hot bath of liquefied paraffin wax is employed,problems of wax decomposition must be dealt with. This decomposition,which is generally considered to be the result of an oxidative mechanismis evidenced by the appearance of undesirable odors, discoloration ofthe wax, and the formation of organic acids, peroxides, and possiblyanhydrides and lactones in the wax. Thus, suppliersof refined paramn waxgenerally recommend that the temperature of a wax melt be kept below 160F. (71 C.) because, beginning at about this temperature, decompositionstarts, accompanied by the development of an acroleinic or burnt odor, asimilar taste and a darkening of the color. Parafiin waxes ranging inmelting point from 59 F. C.) to 176 F. (80 C.) havingfrom fifteen tothirty-five straight chain carbon atoms are readily oxidized in contactwith air above 160 F. By way' of example, after 50 hours at 200 F. a-

2 parafiinwax having a melting point of 122 F. begins to show traces ofperoxides, and after hours at 212 F. a titratable amount of fatty acidhas developed.

Besides the formation of objectionable odors and an increase in colorand acidity, oxidation brings about a lowering of melting point andtensile strength, and an overall deterioration of valuable properties,such as hardness and the like, of the wax. Moreover, when decompositionoccurs, much wax is lost through volatilization and the periodicpurification steps necessitated by this decomposition. Consequently, itis of considerable importance to improve the heat stability of paramnwax.

Wax compositions of improved heat-stability, moreover, offer manyprocessing advantages. Wax coating and impregnating baths may beoperated safely at higher temperatures to effect improved penetration,while allowing better control over the amount of wax pick-up by thepaper or other stock being treated. In addition, entirely newapplications, previously eliminated from consideration because oftemperaturelimitations, become practicable for waxes having improvedheat stability. Furthermore, tank cars may be unloaded more rapidlybecause higher temperatures resulting in lower viscosities give bettertransfer of heat and flow, making possible savings in labor and steamcosts.

A further problem encountered by users of parafiin wax is that ofproviding a finished product, such as waxed paper and beveragecontainers, which will not deteriorate or discolor upon exposure to air.The salability of food products in ,wrappings and containers impregnatedwith wax is adversely afiected by discoloration or yellowing of the waxdue to oxidation. This diificulty becomes more acute with the recentemphasis placed on packaging and package design.

It has been proposed to improve the stability of parafiin waxes againstoxidative deterioration by incorporating therewith one or more materialscalled anti-oxidants because such materials are believed to inhibit theformation of undesirable products of oxidation. However, th inhibitionof parafiin wax against oxidation presents special difiiculties notencountered when choosing an anti-oxidant for other purposes. First, theantioxidant material must be capable of withstanding the temperaturesemployed in wax melts without loss in anti-oxidant powers. This problem,and oxidation conditions in general, are accentuated in the blending ofparaffin wax with higher melting point materials such as polyethylene,as

set forth in application Ser. No. 601,556, filed June 25, 1945, byBowman, Ridenour and Hollenback and assigned to the same assignee as thepresent application. The higher temperatures and agitation employed tendto increase oxidation. Accordingly, anti-oxidants which are suitable inmild temperature applications may not be suitable in paramn wax. Inaddition, an antioxidant must not adversely affect the physicalproperties of the wax.

Where paraffin wax is employed in the manufacture of wrappings,containers, and coatings for foods, an anti-oxidant must not impartcolor, odor, or taste to the Wax, either in the wax melt or when incontact with the food. The standards for paraffin wax are generally muchhigher than for most other products including many edible products suchas edible fats and oils. particularly true with regard to color andodor. Lard oil, for example, has a characteristic odor which althoughnot objectionable from a standpoint of human consumption would be highlyobjectionable if found in paraffin wax compositions. Any color impartedto paraffin wax is highly objectionable from a marketing standpoint and,therefore, a very small degree of oxidation which might give only aslight ofi-white cast to the wax is undesirable, whereas in petroleumoils in general and in many food products a slight discoloration goesunnoticed. Paraffin wax is essentially odorless and, therefore, any odordue to impurity is very easily detected. For example, oxidation ofparafiin wax to such a degree that it has a peroxide number of 0.01 isusually enough to confer a definitely detectable oxidized odor. Such asmall amount of oxidation with its attendant odor may go unnoticed inmany other substances which have some slight characteristic odor oftheir own, the characteristic odor tending to mask the oxidized odor.Since paraffin wax 'is a crystalline material, small amounts ofimpurities can effect relatively large changes in physical propertiessuch as melting point and tensile strength. Small amounts of impuritiesin non-crystalline substances will not exert such a noticeable effect.

The essentially completely odorless and tasteless character of paraflinwax combined with the fact that the oxidation of paraffmic-typecompounds always leads to soluble oxidation products which tend toaffect taste and odor makes the problem of inhibiting paraffin wax onethat is both difficult and unique. The rigid requirements in the tradefor paraliin wax are therefore such that an anti-oxidant for paraffinwax must be effective in very low concentrations where it will not causetaste or odor by itself and at the same time it must, in that lowconcentration, be so effective that the formation of even extremelysmall amounts of odor and taste-producing decomposition products issuppressed.

The question of whether or not any material will satisfactorily functionas an anti-oxidant in any medium is quite unpredictable, for antioxidantaction is highly selective, and apparently catalytic. It is soselective, in fact, that one cannot predict with any degree of certaintythat a material which is a known anti-oxidant for one substance willstill perform as a satisfactory antioxidant in another medium. Forexample, it is well known that many phenolic materials are useful asanti-oxidants for various purposes, but a wide variety of these phenolicmaterials are not suitable as wax anti-oxidants. To illustrate, a numberof phenolic compounds, known to possess This is anti-oxidant propertiesin other environments, have been tested in parafiin wax and found to beunsatisfactory as paraffin wax anti-oxidants. These compounds are asfollows:

2,2-bis (e-hydroxyphenyl) propane;

l.,l-bis (-hydroxyphenyl) cycloliexane;

Orthodihydroxybenzene (catechol) Metadihydroxybenzene (resorcinol) Bis(Z-methoxyphenyl) methane;

2,5-ditertiarybutylhydroquinone;

3 -pentadecylphenol;

Bis (2 hydroxy 3,5 ditertiarybutyl 6 meth ylphenyl) methane;

1,l,2,2-tetrakis (2-methyl-l-hydroxy-5-tertiarybutylphenyl) ethane.

Thus, a material which may be found to exhibit anti-oxidant propertiesin gasoline, for example, cannot on that basis be expected to exhibitantioxidant properties in paraffin wax. Furthermore, it is difiicult topredict that such a material would be otherwise suitable for use in waxcompositions. Apparently, the nature of parafiin wax has considerablebearing on the question.

It is therefore an object of our invention to provide new paraffin waxcompositions having improved stability against general decomposition oroxidative deterioration.

More specifically, a further object of our invention is to provide newparafiin wax compositions of improved heat stability, such as stabilityagainst decomposition in the hot liquefied state.

A still further object of our invention is to provide new paraffin waxcompositions having stability against deterioration due to the action ofair.

Another object of our invention is to provide improved paraffin waxcompositions having good color and exhibiting substantially no odor ortaste, such that they may be employed in food packaging.

These and other objects are accomplished by the present inventionwherein we provide improved paraffin wax compositions comprising a majoramount of a refined paraffin wax and a minor amount, sufficient toinhibit oxidative deterioration, of hydroquinone monobenzyl ether. Thiscompound may be produced by methods well known in the art, and it is awell known commercially available compound.

We have found that the resistance of parafiin wax to oxidation can bematerially increased, and

g the temperature to which it may be heated without breakdown can besubstantially raised by addition to the wax of relatively small amountsof the compound set forth.

This compound can be employed to advantage in paraffin wax stabilizationin amounts ranging from 0.0001 to 0.1 per cent, by weight, of the waxcomposition. A preferred range is from about 0.0005 to 0.01. per cent,by weight, of the wax composition.

The following illustrative examples permit further understanding of ourinvention and show the advantageous results obtained in various waxcompositions containing hydroquinone monobenzyl ether. For the purposesof the following tests, a highly refined paraffin wax having a meltingpoint of 122 F., as determined by A. s. T. M. method D8'7-42, wasemployed. The peroxide number, neutralization number and saponificationnumber, referred to hereinafter, are all obtained by means of standardwell known tests, and are indicative of the degree of oxidative A blendwas prepared employing a 122 F., A. S. T. M. melting point, parafiin waxand 0.001 per cent by weight of hydroquinone monobenzyl ether. Threehundred grams of the blend were placed in a glass oxidation cellsuspended in an I 8 disclosed compound is a remarkably efi 'ectiveparafiin wax anti-oxidant. Furthermore, it is not only'effective forinhibiting oxidation of parafiin wax in the hot liquefied condition, butsince the anti-oxidant is retained by the wax in the finished waxtreated product, the anti-oxidant continues thereafter to perform itsdesired function, and aids in preventing subsequent deterioration of theparaifin wax due to adverse oil bath maintained at 240 Preheated, dry 10conditicns of heat, and the like air at a temperature substantiallytirie same a; The potency as a paraffin wax anfi oxidant $1 Wax g gthrou; of the compound disclosed herein permits of the 8 g l 1 2 g; e gg f g 8 employment of hot baths containing the inhib- 0 u d ti 2 itedparaffin waxes of this invention. In em- EQ a? W1 awn an d g 0 1 i 9 15ploying such baths, it is not necessary to use a 1 1 y F e was 5 2? fi:1 1 8 paraffin wax already containing the anti-oxidant Peroxl es, am 1y Sam 1 a ma y of this invention, but the anti-oxidant can be methodsW611 known 1n the The Odor was added in suitable amounts to the moltenparaffin also notedh table Shows F l wax in the bath in order to preventthe oxidative tained along with data on the uninhibited waxdeterioration thereoi control subjected to the same test conditions.since the anti-oxidant of this invention can TABLE N tr 1' t s d t arriswere mg. KOH mg. KOH Wax gm. wax gm. wax Days Oxidized C 1)121;rolCorlitrol Coilitrol Control 0 u 1 EMP 0. 1 101%, Contml 0. 00%}, 0. 06%,Parafiin Additive Additive Additive It is readily seen that without theanti-oxidant additive of our invention all three measures of oxidativedeterioration, viz., the peroxide number, neutralization number, andsaponification number, increased rapidly with time, whereas values forthe sample which contained the antioxidant showed no change even after 7days. The initial rise and subsequent drop in peroxide value for theuninhibited control sample is typical of wax oxidation.

The uninhibited wax developed a strong oxidized odor on the second dayof the test, but the inhibited composition did not develop such an odorfor the full '7 days of the run.

Example II Another blend was made employing 0.001 per cent by weight ofhydroquinone monobenzyl ether in a 122 F., A. S. T. M. melting point,parafiin wax. One hundred grams of this composition was placed in aglass tumbler covered with a watch glass in an oven maintained at 180 F.Once every 24 hours the sample was examined for the presence of anoxidized odor.

The test was terminated at the end of 60 days, at which time, the samplewas still free of oxidized odors. The uninhibited wax control, in thesame test, developed a strong oxidized odor in from 1 to 4 days, showingthat the additive was very effective even at the low concentrationemployed.

The above specific examples clearly demonstrate the efiicacy, as aparaffin wax antioxidant, of hydroquinone monobenzyl ether. The completelack of change in peroxide, neutralization and saponification numbers,coupled with the lack of odor formation after subjection of theinhibited parafi'in wax to severe oxidative environment indicate beyondany doubt that the be employed so effectively in relatively smallamounts, it does not affect the odor and taste of the parafiin waxeswithwhich it is incorporated, and similarly, none of the desirable physicalproperties of the wax such as melting point and tensile strength areadversely affected.

As will be understood by those skilled in the art, the stabilizedparaifin wax compositions of our invention may contain other additivesand ingredients blended therewith to improve other characteristics, suchas tensile strength, sealing strength, etc, of the composition.

While our invention has been described above with reference to variousspecific examples and embodiments, it will be understood that theinvention is not limited by such examples and embodiments, but thatresort may be had to such modifications and variations as fall withinthe spirit of the invention and the scope of the ap-- pended claims. Weclaim:

1. An improved wax composition comprisinga major amount of a paraffinwax and a minor amount, sufiicient to inhibit oxidative deteriora:

tion, of hydroquinone monobenzyl ether.

2. The composition of claim 1, wherein the. said ether is present in anamount of from about.

0.0001 to 0.1 per cent, by weight.

3. An improved wax composition comprising; a major amount of a paraffinwax and from about-. 0.0005 to'0.01 per cent by weight, of hydroquinoneReferences Cited in the file of this patent UNITED STATES PATENTS 7Number Name Date 2,116,220 Shoemaker May 3, 1 938 FOREIGN PATENTS NumberCountry Date 581,747 Great Britain Oct. '23, 1947 V

1. AN IMPROVED WAX COMPOSITION COMPRISING A MAJOR AMOUNT OF A PARAFFINWAX AND A MINOR AMOUNT, SUFFICIENT TO INHIBIT OXIDATIVE DETERIORATION OFHYDROQUINONE MONOBENZYL ETHER.